Preheat the oven to 200C/400F/Gas 6. Grease a 12-hole muffin pan well, then set aside.
Whisk together the flour, sugar, baking powder, baking soda, and salt. Set aside.
Whisk together the eggs, oil, yogurt, and vanilla extract. Pour the wet ingredients into the dry ingredients, and mix until just combined. Do not over-mix. Gently fold in the strawberries.
For the Streusel
In a small bowl, whisk together the flour, sugar, and cinnamon. Add the melted butter, and mix until evenly distributed.
Spoon the batter into the prepared pan, top with the streusel, and bake for 15 - 20 minutes, or until a toothpick inserted into the centre comes out clean. Allow to cool for 5 - 10 minutes in the pan, then transfer them to a wire rack to cool completely.
Video
Notes
Muffins stay fresh in an air-tight container at room temperature for up to 5 days. They also freeze well for up to 2 months. Thaw overnight in the fridge.